1. Field of the Invention
The present invention relates to a process for manufacturing a sifting device having slit-shaped openings. The process may include forming insets (e.g., recesses or openings) in at least one support element, inserting a plurality of rods, substantially parallel to each other, in the at least one support element and forming filtering slits (or gaps) between the rods. The rods may be permanently bonded in insets of the at least one support element with a bonding agent. The inserted rods may have a shape or profile to securely hold a position of the rods within the at least one support element during subsequent manufacturing.
An example of an application for a sifting device, such as the device to be manufactured by the above process, may be in sorting fiber pulp suspension. The fibers contained in a suspension pass through a sieve while undesired solid constituents are shunted off or diverted by the slit and removed from the sifting device. An application for the separation of different fiber constituents is also conceivable. The suspension may include similar contents of fibrous particles and cubical particles, however, the fibrous particles may pass more easily through the sieve than the cubical particles because the openings may be substantially longitudinal in form, e.g., as slits or gaps. Further, very good separation of non-fibrous interfering materials from fiber suspensions may be possible with separation technology of this type. However, high-precision slit-shaped openings over the entire sifting surface may be necessary.
2. Discussion of Background Information
DE 39 27 748 A1 describes a process, similar in general to the above described process, that produces a strainer basket in which rod sections are fastened by a plastic deformation of retainer rings with insets for the rods. Specially designed rod sections, having a predetermined profile or shape, are used in production processes of this type. With the aid of this process, it is possible to reduce production costs significantly. However, strainer baskets of this type suffer from several drawbacks and limitations.
Sieves and strainer baskets with good stability and high surface quality can be produced according to a process that is described in DE 42 14 061 A1. A high-temperature soldering process is used to mount the rod-like sections. The results are favorable, however, the process is laborious and expensive.
Sieves and strainer baskets similar in general to the above described devices have been discussed in German patent document DE 33 27 422 A1 in which filter slits are shaped by essentially parallel rod-like sections welded to support transverse ribs. However, this process makes it difficult to firmly mount the rods and support ribs. Further, even if a firm mount of the rods to the support ribs is made, the substantial cost due to the precision requirements prevents this process from being preferable because all material surfaces that contact the pulp have to be extremely smooth to avoid the adhesion of fibers to the sifting device during operation. This is the best manner for preventing accumulation and clogging of fibers at this location. Although it has been suggested that such weld seams could later be smoothed or covered, such measures generally only serve to increase production costs.